"Total nonsense and laughably false as anybody who would speak on the record would tell you. Absurd," Costolo posted on Twitter on Thursday.

"Shows a lack of understanding of the very basics of how trust and safety works at Twitter. Sensationalist nonsense."

It's not immediately clear whether Costolo is denying claims that he censored tweets, or objecting to the critical thesis of the report more generally. The former executive did not immediately respond to Business Insider's request for clarification on Twitter, and did not respond to BuzzFeed's requests for comment as the report was being written.

Twitter has long been regarded as having a serious problem with harassment and abuse — an issue that was thrown into sharp relief in recent months after "Ghostbusters" actress Leslie Jones was subjected to a torrent of racist and sexist abuse that culminated in the banning of a conservative journalist, Milo Yiannopoulous, from the site. (Disclosure: I previously worked for Yiannopoulous' tech site, The Kernel, in 2013.)

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